The present invention relates generally to electric submergible pumping systems, and particularly to bearing systems for improving the wear characteristics of a submergible motor implemented in the electric submergible pumping system.
Pumping systems, such as electric submergible pumping systems, are utilized in pumping petroleum and/or other production fluids from wells. A typical electric submergible pumping system includes components, such as a submergible motor, a motor protector and a submergible pump for producing fluids to the surface of the earth. Each of the submergible components has moving parts that are subject to wear. For example, one area subject to wear is within the stator, and specifically at a rotor bearing used to rotatably support an axial shaft within the submergible motor.
Typically, a submergible motor is designed with a shaft rotatably mounted in at least one support bearing disposed within an internal bore or opening through the stator. For example, bronze bearing sleeves have been used for rotation within a steel bearing. However, such combination is readily galled by dirt or boundary lubrication. This wear can lead to rubbing or scraping of the rotor against the stator, resulting in friction, wear, overheating, and eventual short circuit of the motor. Steel bearings, on the other hand, are slightly induction driven and subject to heating, even when bronze stator laminations are used at the bearing location.
In other applications, hard, non-magnetic (Stellite(trademark)) bearings have been used with all steel laminations, but the use and formation of such materials tends to be very expensive. Soft, non-magnetic bearings, however, tend to incur galling proximate the stator bore.
Another reason conventional bearings have been unsatisfactory is that the bearings tend to spin within the stator bore creating detrimental wear areas on the stator. The impetus for bearings to spin include electromagnetic induction, oil shear, thrust friction, and bushing friction. Attempts have been made to prevent the bearing from spinning within the stator bore, but those attempts have proved expensive, unreliable, damaging to the laminations and often difficult to assemble.
It would be advantageous to have a dependable, economical bearing system for use in submergible motors and electric submergible pumping systems that would prevent rotation of the bearing relative to the inner wall of the stator.
The present invention features an electric motor comprising a housing, a stator mounted within the housing, and a shaft rotatably mounted within the housing. The motor further comprises a rotor bearing disposed between the stator and the shaft. The rotor bearing includes a bearing sleeve mounted adjacent the shaft and a main body portion disposed in sliding engagement with the bearing sleeve. A spring mechanism is engaged with the main body portion, and a bracelet is disposed around the spring mechanism intermediate the spring and the stator. The spring biases the bracelet against an internal wall of the stator to limit rotation of the bearing with respect to the stator.
According to another aspect of the present invention, a rotor bearing is provided for use in an electric motor. The motor is of the type having a rotor mounted on a rotatable shaft within a center bore or opening of a stator. The rotor bearing includes a main body portion, a spring mechanism and a bracelet. The main body portion has a radially inward contact surface that slidingly engages a bearing sleeve mounted to the shaft. The spring mechanism is disposed about the main body portion, and the bracelet is pressed between the spring mechanism and the stator.
According to another aspect of the present invention, a submergible pumping system is provided for use in a wellbore. The pumping system includes a submergible pump, a submergible motor protector, and a submergible motor. The submergible motor includes a housing, a stator and a shaft rotatably mounted within the stator. The motor further includes a rotor bearing disposed between the stator and the shaft. The rotor bearing includes a bearing sleeve, a main body portion, a spring mechanism, and a bracelet. The bracelet is disposed about the spring mechanism between the spring mechanism and an interior surface of the stator. As the shaft rotates, the bearing sleeve slides against an interior surface of the main body portion, and the spring mechanism forces the bracelet to an expanded position against the interior surface of the stator to prevent rotation of the main body portion with the shaft.